Variable condenser



Dec. l3, 1927.

J. D. SARTAKOFF VARIABLE CONDENSER Filed Sept. 29, 1925 1 1V V E N T 01? Am? i farzaka/f ATT R ill l atented lilac, T13, 1927.

- STAES 35.013. ll). SARTAKOFF, 0F NEW,YORK, N.-Y,, FORMATION, OF NEW YORK, N. Y.,

in an hell 0 ASSIGNOB OF ONE-HALE TU A CGRFOlR-ATIPION 0F NEW VAEIAHLE' DENSER.

a nsiida filed Septemhlar senses. serial no. cases.

embodies two plates adapted for relative rectangular movement in an axial direction. to vary the capacity, and between these plates I employ both air and a solid substance as dielectrics. The solid substance positively precludes contact between the plates with consequent short circuiting of the condenser. Both the plates and the solid dielectric are provided with plane surfaces and the said dielectric is permanently secured to one of said-plates to irisure uniformity of operation of the structure.

in practically carrying out the invention, a threaded connection is provided between the plates so that when one is rotated, theyare shifted toward. or away from one another to effect the change in capacity; 1 However, as the plates come into close proximity, the movable one engages the solid dielectric and further movement in this direction is arrested so that the plates cannot possibly contact with one another. 1

ln its preferred, practical form, the condenser embodies a hollow insulating casing, one side ofwhich is closed by a metal plate, This plate is permanently secured to the casing and overthe innerysuriace of said plate is a sheet of solid dielectric substance which is adhesively secured to the plate throughout and ispreferably clamped at its edges between the plate and casin Positioned within the casing and coaxial with the fixed plate, a movable metal plate which has a stem or spindle projecting through the closed end, of the casing is adapted. to receiveand carry a suitable dial. The movable plate has threaded connection with and. this bushing is rigidly fixed to the casing so that rotation ot the spindle will shift it longitudinally to varylhe distance between the plates. A stop is provided on the spindie to coact with a stop on the casing to limit the rotation of the spindle to the desired range, With this arrangement, all the operating parts except the projecting portion of the spindle are housed within dust and moistureproof casing and will be i'nlly protected thereby.

Featuresof the invention, other than those adverted to,-w1ll be apparent from the hereinafter detailed description and claims, when i read in conjunction with the accompanying drawings.

The accom anying' drawings illustrate one 7 practical em odiment of the invention, but the construction therein shown is to be understood as illustrative, only, and not as defining the limits of the invention.

The drawing shows a section through the condenser embodying the present invention,

Referring to the drawings, 1 designates a casing of insulating material, such, for enample, as bakelite, composition oil hard rubher or the like. The casing is, in practice,

preferably made circular in cont-our and is hollow as shown in the drawings. lit is provided with a substantially closed side 2 torming'wit-hin the casing a chamber 3. Preferably molded integral with the casing are attaching posts a, which are adapted to receive screws 5, whereby the device may be mounted on a. panel'oi a receiving set The open sideot the casing is closed y a metal plate 6, the inner surface of which is covered by a sheet of solid dielectric Z, The sheet '5 maybe any suitable dielectric, and this sheet is permanently secured to the plate 6 throughout its entire extent, so as to hol the sheet firmly to the plate throughout and. preclude buckling or wrinkling or? the sheet. lln practice, ll preferably extend the sheet to the outer periphery of the casing and clamp the margin of such sheet tightly in position by means of the screws 8, which bind the plate 6 to the casing. 9 designates the movable plate of the condenser. it is fell of metal and is provided with a spindle l0,

. varied.

' ing. The collar may be positioned to permit c the distance between said movable plate and the fixed plate in order that the capacity of the condenser may be The plates are included in circuit in any suitable manner as by a binding screw with a fixed plate and a h rush or pigtail contact with the spindle of the movable plate.

1 preferably associated with the spindle means for limiting its rotation within, predetermined limits and a very convenient form of this means consists in a metal collar 17 carrying a radial linger 18 adapted to copurpose of varyii operate with a suitable fixed stop. A stop 19 is shown as a'post mounted on the casot the desired adjustment of the movable plate and a set screw thereupon tightened to lock the collar against shifting so that thereafter the plate will move within fixed and predetermined limits.

The construction, which I have described, possesses marked advantages. For example. it will be apparent that a very fine adjustment of the distance between the plates can he obtained. Moreover, all of the operating parts except the projecting portion of the spindle are housed within the insulating, casing which not only serves to support all of the parts, but also forms a dust proof and moisture proof housing.

The solid dielectric sheet 7 positively preeludes engagement between the fixed and movable plates since after the plate 9 has been screwed down sufiiciently to come in contact with the dielectric sheet, a further movement of this plate in the direction of the fixed plate is precluded. It will be apparent,

, however, that, under ordinary conditions, of

operation covering the wave length band of broadcasting, the movable plate will generah ly be free from engagement with the sheet 7 so that the condener will function as a com bined air condenser and solid dielectric.

Careful experimentation andtests have shown that a great range of capacities and frequencies can be covered by this condenser and that the frequency has unusually straight line characteristics. 7

The accompanying drawings showthe invcntion in its preferred practical form, but the invention is to be understood as fully commensurate with the appended claims.

Having thus fully described the invention. what 1 claim as new and desire to secure by Letters Patent is:

l. A variable condenser embodying a hollow casing; of insulating material having a threaded circular interior, open at one side and provided at its opposite side with an axial opening, a metal platelixed to the open side of the casing and rigid therewith, a solid dielectric overlying the inner face of said plate and rigidly secured thereto throu 'hout its extent and clamped at its margins tween the plate and casing, and a movable plate positioned within the casing and havinn a'spindle extending through the opening of thecasing, and said movable plate having a threaded periphery engaging with the threads of the interior of the casing, whereby rotation of the spindle results in the shifting of the movable plate toward or away from the fixed plate to vary the capacity.

2. A variable condenser embodying a hollow casing of insulating material having a threaded circular interior open at one side and provided at its opposite 'side with an axial o cning, a metal plate fixed to the open si e of the casing and rigid therewith, and a movable plate positioned within the using and havihg a spindle I extending through the opening of the casing, and said movable plate having a threaded periphery engaging with the threads of the interior of the casing, whereby rotation of the spindle results in the shifting of t-he movable plate toward or away from the fixed plate to vary the capacity.

In testimony whereofl have signed the foregoing specification.

JACK D. SARTAKOFF. 

